Sleep is a naturally occurring, periodic, reversible state of unconsciousness that is ubiquitous in mammals and birds, although its precise function is not known. The importance of sleep is suggested by its homeostatic regulation: the longer an animal is awake, the more it needs to sleep.
In humans, obtaining less than the required number of hours of sleep, particularly over several nights, leads to a decreased ability to retain new information, impaired productivity, altered mood, lowered resistance to infection and an increased susceptibility to accidents. Sleep-related traffic accidents annually claim thousands of lives, and operator fatigue has also been shown to play a contributory role in airplane crashes and other catastrophic accidents.
Besides lifestyle factors, a variety of physiological and psychological disorders can affect sleep patterns. The most common sleep disorder is primary insomnia, or a difficulty in initiating or maintaining sleep, which affects a large percentage of the population at some point in their lives. Other common sleep disorders include hypersomnia, or excessive daytime sleepiness, and narcolepsy, which is characterized by sudden and irresistible bouts of sleep.
Currently available drugs used to modulate vigilance, such as drugs that induce sleep, prolong wakefulness, or enhance alertness, suffer from a number of shortcomings. For example, available sleep-inducing drugs often do not achieve the fully restorative effects of normal sleep. Often such drugs cause undesirable effects upon waking, such as anxiety or continued sedation. Many available drugs that increase vigilance do so with a characteristic “crash” when the effect of the drugs wears off. Furthermore, many of the currently available drugs that modulate sleep and wakefulness are addictive or have adverse effects on learning and memory.
Clearly, there is a need to identify drugs that induce restorative sleep or that increase vigilance, without undesirable side effects. Unfortunately, current methods for screening for such drugs, using mammals, are slow, burdensome and expensive. Thus, there exists a need for improved methods for screening for drugs that modulate sleep and vigilance. The present invention satisfies this need and provides related advantages as well.